Spatial Power Combining and Splitting in Gap Waveguide Technology

A realization of the quasi-optical (QO) feed concept for linear millimeter-wave (sub-)array antennas is demonstrated in gap waveguide technology. The proposed feed architecture employs an input transition from a ridge gap waveguide (RGW) to a groove gap waveguide (GGW), a radial (H-plane sectoral) GGW section, and a transition to an output RGW array. A design decomposition approach is presented to reduce simulation complexity. Several 20-element QO feed implementations are investigated at W-band demonstrating a 20% relative bandwidth (85–105 GHz), 0.5 dB insertion loss, and a capability of an amplitude taper control within the 10–20 dB range.

This paper describes a simple, low loss, compact tuneable band pass filter based on ridge gap waveguide (RGW) technology for the Ku-band applications. This is achieved by keeping the height of the air gap in the gap guide structure equal to the thickness of the substrate or base of the structure. The resonant frequency and electromagnetic (EM) field distribution of the structure is investigated. This filter is designed by inserting the proposed ridge in the cut-off region of the gap waveguide. The frequency of tuning has been carried out using the slot created on ridge, which generates capacitive effect. Experimental results of the manufactured structure show an insertion loss of approximately 0.15 dB and a return loss of 16.38 dB over 4.5% relative bandwidth in Ku-band. The structure, put forwarded here, has been designed and optimized in the CST microwave studio environment and simulated results are validated by experimental results. The size of the structure is 64.65 mm × 64.65 mm × 7 mm.

This article presents the design of a flat Luneburg metalens antenna at V-band using gap waveguide (GW) technology. The metalens consists of a parallel plate waveguide (PPW) loaded with metallic pins whose height is modulated to get an effective refractive index that follows the Luneburg equation. A Groove GW (GGW) H-plane horn is used to illuminate the metalens, such that the rays are collimated and a planar wavefront is generated in the direction of propagation. Since the structure at hand is planar, it can be efficiently integrated on flat surfaces. Moreover, the fully metallic structure is mechanically robust and presents lower losses than lenses including dielectric substrates. A prototype has been fabricated and tested, simulations and experimental results are in very good agreement. The metalens yields an input reflection coefficient ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$S_{11}$ </tex-math></inline-formula> ) below −10 dB from 45 to 70 GHz, whereas the −3 dB gain fractional bandwidth is 26.2% with respect to a center frequency of 60 GHz, with a peak of 22.5 dB at 61 GHz. These features make this design an interesting solution for millimeter-wave (MMW) applications.

A low insertion loss wideband mm-Wave crossover with three-section branch-line structure based on ridge gap waveguide technology

A novel substrateless power amplifier module realized by ridge gap waveguide (RGW) technology is proposed in Ka-band. Up to our knowledge, this is the first time that an active device is directly integrated with an RGW structure. No substrate is used in the RF section of the implemented power amplifier and the whole structure is made by machining a piece of metal. The amplifier was made of two pieces and was easily assembled without needing a precise contact between the two sections. The cavity resonance of the amplifier is suppressed using a pining structure. The fabricated amplifier module is self-packaged and does not need any packaging. It is shown that the simulated and measured results are in good agreement. This paper shows the capability of RGW technology for implementing the whole RF frontend in microwave- and millimeter-wave systems.

In this article, a slot array with double-layered full-corporate-fed distribution network by ridge gap waveguide (RGW) in the G-band is presented. The array antenna proposed in this article contains 16 × 16-element radiation slots fed by air-filled ridge gap waveguide distribution network that achieves high-efficiency. Gap waveguide technology avoids the demand for perfect electrical contact in millimeter waves, therefore the expensive diffusion bonding and the laser welding processes are not demanded. Moreover, the high-accurate Computerized Numerical Control (CNC) machining is applied for the fabrication. Due to the limited layout space for the distribution network, two types of universal stepped cavity power dividers are presented in this article. The proposed array antenna is fed by a standard WR-5 waveguide at the bottom. Furthermore, the tested outcomes show that the proposed 16×16-element array has a gain larger than 30 dBi with over 50% antenna efficiency in the frequency range of 155-171 GHz.

The Gap Waveguide technology utilizes an Artificial Magnetic Conductor (AMC) to prevent the propagation of electromagnetic (EM) waves under certain conditions, resulting in various gap waveguide configurations. In this study, a novel combination of Gap Waveguide technology and the traditional coplanar waveguide (CPW) transmission line is introduced, analyzed, and demonstrated experimentally for the first time. This new line is referred to as GapCPW. Closed-form expressions for its characteristic impedance and effective permittivity are derived using traditional conformal mapping techniques. Eigenmode simulations using finite-element analysis are then performed to assess its low dispersion and loss characteristics. The proposed line demonstrates an effective suppression of the substrate modes in fractional bandwidths up to 90%. In addition, simulations show that a reduction of up to 20% of the dielectric loss can be achieved with respect to the traditional CPW. These features depend on the dimensions of the line. The paper concludes with the fabrication of a prototype and validation of the simulation results in the W band (75-110 GHz).

A broadband 3-way power divider based on gap waveguide for Ka-band applications

High-efficiency single-layer corporate-feed gap waveguide based circularly polarized antenna array with compact size

This article presents a wideband design of a rotary joint based on groove gap waveguide technology. The proposed design includes two coax-to-groove gap waveguide (GGW) transitions, connected together in a back-to-back arrangement. As the gap waveguide structure does not require electrical connections between different parts, the rotor part is placed on top of the stator with an air gap distance while the wave leakage is suppressed. Therefore, the rotating choke, which is a critical and bulky part in the previous designs, is eliminated. By introducing some matching posts in the structure, a wideband design is achieved with 55% bandwidth covering from 11 to 19.5 GHz, where the insertion loss is lower than 0.28 dB. Some parameter sweeps are presented to investigate the effect of the rotor displacement during rotation. A prototype of the proposed rotary joint was fabricated using CNC milling for verification of the design. The measured results agree well with the simulated ones and prove the excellent performance of the proposed rotary joint.

This paper presents a Ka-band linearly-polarized 4-antenna array fed with a novel corporate distribution network that uses a half-mode groove gap waveguide (HM-GGW). The antenna feed has no contact with the top cover where the array antenna is located, thanks to the features inherent in gap waveguide technology (GW). This technology, with many advantages, sometimes suffers from a complex mechanization, which in this case is reversed by the novel network proposed in this paper.

In this paper, a W-band high gain 4×4 slot-enhanced antenna array is proposed based on ridge gap waveguide (RGW). The antenna array is composed of four 2×2 slot-enhanced antenna subarrays, and each subarray is excited by a high-order mode TE220 within a substrate integrated waveguide (SIW) cavity using PCB technology. The feeding network based on ridge gap waveguide (RGW) can reduce the transition loss. The gain of the designed antenna is more than 18 dBi and the peak gain reaches 19.7 dBi for the impedance bandwidth.

Due to structural and aerodynamic limitations, conformal antennas are increasingly sought after in antenna design. Gap waveguide technology has also gained traction for its potential in leaky wave antenna development. This paper proposes a novel conformal leaky wave antenna utilizing this emerging gap waveguide technology. Prior research has not extensively explored the radiation characteristics of such antennas on curved and conformal surfaces. This work addresses this gap by investigating the design procedure, radiation mechanism, and optimization methods for leaky wave antennas on conformal surfaces. The proposed antenna achieves a gain of approximately 18 dB and a scanning angle ranging from 1 to 33 degrees within the frequency band of 9.5 GHz to 12 GHz. Fabrication and subsequent measurements of the antenna were conducted, with the results demonstrating good agreement with the simulations.

In this paper a new ridge gap waveguide working in 3.5–5GHz has been designed. It is excited by coaxial line transition. In the beginning, this paper simply describes the basic principle related to electromagnetic band-gap (EBG) or artificial magnetic conductor (AMC) to explain why only local quasi-TEM modes can propagate in the designed waveguide. The principle performance of the ridge gap waveguide is explained by numerical simulations of the dispersion diagram. Through comparing and analyzing the influence of some parameters we determine the structure of the ridge gap waveguide. The numerical simulation and experimental validation have been shown in this paper and the result of measurement is better than the simulated result in the range of 3.5–5GHz.

A 2×2 circularly polarized (CP) patch subarrays based on ridge gap waveguide (RGW) around 30GHz is designed. To broaden the CP bandwidth, the 2×2 patch subarray elements are fed by sequential feeding technique. The simulated results using CST show that the RGW feeding has a great performance in terms of impedance and radiation characteristics so that impedance and CP bandwidths are 30.5% and 21.5% respectively. In addition, a peak gain 13.5dB at 30GHz is achieved. Numerical results indicate that the proposed structure can cover the 3dB-gain bandwidth of 22.1%.